The present invention relates to testing of a radio frequency (RF) data packet signal transceiver, and in particular, to testing such a device via a wireless signal path.
Many of today's electronic devices use wireless signal technologies for both connectivity and communications purposes. Because wireless devices transmit and receive electromagnetic energy, and because two or more wireless devices have the potential of interfering with the operations of one another by virtue of their signal frequencies and power spectral densities, these devices and their wireless signal technologies must adhere to various wireless signal technology standard specifications.
When designing such wireless devices, engineers take extra care to ensure that such devices will meet or exceed each of their included wireless signal technology prescribed standard-based specifications. Furthermore, when these devices are later being manufactured in quantity, they are tested to ensure that manufacturing defects will not cause improper operation, including their adherence to the included wireless signal technology standard-based specifications.
For testing these devices following their manufacture and assembly, current wireless device test systems typically employ testing subsystems for providing test signals to each device under test (DUT) and analyzing signals received from each DUT. Some subsystems (often referred to as “testers”) include at least a vector signal generator (VSG) for providing the source signals to be transmitted to the DUT, and a vector signal analyzer (VSA) for analyzing signals produced by the DUT. The production of test signals by the VSG and signal analysis performed by the VSA are generally programmable (e.g., through use of an internal programmable controller or an external programmable controller such as a personal computer) so as to allow each to be used for testing a variety of devices for adherence to a variety of wireless signal technology standards with differing frequency ranges, bandwidths and signal modulation characteristics.
During manufacturing, the testing of such wireless devices (i.e., prior to full assembly including the system housing, or case, and antenna system, which can involve one or more antennas depending upon modes of wireless operations) typically involves conveyance of test signals between the tester and DUT via conductive signal paths, such as RF cabling and connectors (e.g., coaxial). Later, after full assembly, further tests are typically performed to make sure that the antenna system and connections (signals and power) are operating properly and that no other post-assembly defects (e.g., electronic, mechanical or electro-mechanical) have occurred.
Proper operation of a fully assembled DUT can be determined by a combination of DUT receiver and transmitter tests where the receiver sensitivity (e.g., measured in terms of bit error rate (BER) or packet error rate (PER), defined as the number of incorrectly received data bits or packets divided by the total number of transmitted bits or packets, respectively) is better (i.e., lower) than a specified value, and transmitter power output is found to be within a desired power range. However, determining receiver sensitivity and/or transmitter output power accurately in a wireless test environment (e.g., a testing environment involving radiative conveyance of test signals between the tester and DUT) tends to be problematic due to sensitivity of the positioning of the DUT within the test environment caused by variables associated with distances between the tester and DUT antennas, such as signal attenuation and multipath effects.
To avoid these testing issues, while conductive signal paths could be used, such testing techniques cannot be used to include effects from wireless signal issues associated with antenna systems and connections.
It would be desirable to enable testing of receiver sensitivity and transmitter power levels, which tend to be indicative of manufacturing or assembly-related defects, and to do so without first needing to, somehow, determine absolute signal loss within the wireless signal path, particularly since such signal path loss will change even with small changes in positioning of the DUT relative to the tester. Accordingly, a testing method that can identify defects in either receiver sensitivity or transmitter output power levels, or both, following full DUT assembly, without requiring determination of absolute signal path loss will require fewer testing steps and reduce testing costs while also preserving test accuracy and integrity.